The invention discloses a preparation method of an ammonium glyphosate technical product. The method at least comprises the following steps: adopting the method that N-phosphonomethyliminodiacetic acid is processed by catalytic oxidation to prepare glyphosate to obtain the mixed liquid of glyphosate and solid catalyst; injecting ammonia in the mixed liquid to react; performing hot filtering to the reaction liquid, performing vacuum concentration to the filtrate, performing low-temperature filtration to obtain filter cake; washing the filter cake with organic solvent and drying to obtain the ammonium glyphosate technical product. The invention has less steps, the separation process of solid glyphosate and solid catalyst and the preparation process of ammonium glyphosate are combined to onestep; the reaction yield is high, the production cost is effectively reduced; and formaldehyde in the glyphosate mixed liquid reacts with ammonia to prepare a by-product of urotropine, urotropine canbe recycled with water, and wastewater can not be discharged in the whole process, thus the environment is protected. The product of the invention has high purity, the content of ammonium glyphosate in the ammonium glyphosate technical product is not less than 98.5%, the heating loss is not more than 1.0%, and the glyphosate content is not less than 89.5%.